In a general electrophotographic process, an electrophotographic photoreceptor undergoes processes including at least cleaning, charging, light exposure, development, and image transfer. In each process, the photoreceptor is subjected to treatments by means of, for example, a cleaning blade for removing toner remaining on the surface of a photoreceptor drum, a conductive roller for uniformly imparting electric charge to the photoreceptor, and a transfer belt for transferring a toner image. From the viewpoints of plastic deformation and wear resistance, the cleaning blade is usually produced from a thermosetting polyurethane resin.
However, when a cleaning blade formed of polyurethane resin is used, the friction coefficient between a blade member and a photoreceptor drum increases, whereby defoliation of the blade or generation of anomalous sounds occurs. In such a case, the drive torque of the photoreceptor drum must be increased. In addition, in some cases, the edge of a cleaning blade is adhered to a photoreceptor drum or the like, resulting in drawing and cutting, whereby the edge of the cleaning blade may be damaged through wearing.
In order to solve such problems, efforts have been made for providing a contact part of the polyurethane blade with higher hardness and lower friction. In one proposed method, a polyurethane-made blade is impregnated with an isocyanate compound, to thereby cause reaction between the polyurethane resin and the isocyanate compound, whereby the hardness of the surface the polyurethane resin blade and a portion in the vicinity the surface of the blade are selectively increased, and their friction is reduced (see, for example, Patent Document 1).
However, when the surface of the blade is enhanced, chipping of the blade problematically occurs. Also, although reducing the friction of the blade surface can prevent occurrence of filming (i.e., a phenomenon of toner adhering onto a photoreceptor drum), undesired release of toner tends to occur, problematically resulting in cleaning failure.
Another proposed cleaning blade has specific properties including dynamic hardness and friction coefficient of the polyurethane resin blade surface (see, for example, Patent Documents 2 to 5). However, even though properties including dynamic hardness and friction coefficient of the polyurethane resin blade surface are limited, a satisfactory blade has not been always realized, and generation of chipping and filming after long-term use cannot be satisfactorily suppressed.